In recent years, with the spread of computers, ink jet printers have come into wide use for printing on paper, film or cloth not only in offices but in individual houses as well.
Ink jet recording methods include a method of ejecting liquid droplets by applying pressure through piezo elements, a method of ejecting liquid droplets by generating a bubble in an ink through heat, a method of using ultrasonic waves and a method of attracting and ejecting liquid droplets by electrostatic power. As an ink for these ink jet recording methods, there are used aqueous inks, oily inks or solid (melting type) inks. Of these inks, aqueous inks are mainly used in view of productivity, handling properties, smell and stability.
Colorants to be used in these inks for jet recording methods are required to have a high solubility in a solvent, realize high-density recording, provide a good hue, have excellent fastness against light, heat, air, water and chemicals, show an enough good fixability for an image-receiving material not to be blurred, have an excellent keeping quality as an ink, have no toxicity, have a high purity and be available at a low price. However, it is extremely difficult to find colorants satisfying these requirements at high levels. In particular, colorants having a good yellow hue and an excellent light fastness have eagerly been desired.
Various dyes and pigments have already been proposed and have been practically used as colorants for ink jet recording but, up to now, there have been found no colorants which satisfy all of the requirements. It is difficult for those dyes and pigments which have conventionally been well known and which respectively have Color Index (C.I.) numbers to simultaneously satisfy the requirements for hue and fastness required for an ink for ink jet recording. Japanese Patent Laid-Open No. 212566/1990 discloses an ink jet ink intended to satisfy requirements for both hue and light fastness.
However, dyes used in the publication is insufficient with respect to improvement of hue and light fastness. The dyes described in the publication also involve problems with respect to moist heat fastness. Also, Japanese Patent Laid-Open No. 22714/1992 discloses thiadiazolyl-azo-pyrazole yellow dyes as dyes for thermal transfer recording. However, the dyes have such an insufficient solubility in an aqueous solution that they cannot be used in a water-soluble ink for ink jet recording.
On the other hand, Japanese Patent Laid-Open No. 74761/1983 and Japanese Patent Laid-Open No. 92369/1985 describe inks comprising a dye, glycerin and an ethylene oxide adduct of diethylene glycol or an alcohol and, further, Japanese Patent Laid-Open No. 265098/2000 describes to use an ethylene oxide adduct of a long, straight-chain alcohol. However, these techniques are still insufficient and involve the defect that image quality of a formed image will be deteriorated during storage.
In addition, Japanese Patent Laid-Open Nos. 88048/1993, 333532/1996 and 333533/1996, and U.S. Pat. Nos. 5,837,043 and 5,626,655 propose that blurring of an image can be reduced by an ink using an ethylene oxide adduct of a higher alcohol. However, this technique has the defects that the ink is liable to cause clogging and that image preservability of a printed image is so poor that the image suffers change in color tone.